1. Field of the Invention
The present invention relates to a method of fabricating a light emitting diode, and more particularly to a method of fabricating a light emitting diode that has an inclined sidewall to improve light emitting efficiency.
2. Description of the Related Art
Light emitting diodes (LEDs) are photoelectric transformation elements with a structure in which a P-type semiconductor is joined to an N-type semiconductor to emit light via recombination of holes and electrons in a junction between the P-type semiconductor and the N-type semiconductor by application of forward bias. Since colors of light emitted from the LED depend on the band-gap energy of the semiconductors, the LED for emitting light of an intended color can be fabricated through proper selection of semiconductor materials.
The LEDs enable exhibition of various colors by emitting light of various colors and are widely applied to display devices and backlights for various electronics, instrument panels, electronic display boards, etc.
Additionally, since the LEDs have lower power consumption and longer lifetime compared with conventional lighting instruments, such as incandescent lamps or fluorescent lamps, they are replacing the conventional light instruments and increasing in use for general lighting applications. However, for the LEDs to be used for the general lighting applications, it is very important to improve light emitting efficiency of the LEDs, and various techniques have been developed for this purpose.
FIG. 1 is a schematic cross-sectional view of a conventional light emitting diode.
Referring to FIG. 1, the conventional LED 1 comprises semiconductor layers 16 formed on a substrate 11. The semiconductor layers 16 comprise an n-type semiconductor layer 15, an active layer 17, and a p-type semiconductor layer 19 sequentially stacked on the substrate 11. Additionally, the LED 1 generally comprises a buffer layer 13 formed between the substrate 111 and the N-type semiconductor layer 15 to relieve lattice mismatch therebetween, and a metal layer 21 on the p-type semiconductor layer 19.
The metal layer 21, p-type semiconductor layer 19, and active layer 17 formed on the N-type semiconductor layer 15 are sequentially etched to expose an upper surface of the N-type semiconductor layer 15, followed by respectively forming pads 23 and 25 on the upper metal layer 21 of the p-type semiconductor layer 19 and on the exposed N-type semiconductor layer 15 to form a metal wire on the LED 1.
With such a structure, the conventional LED has sidewalls vertical to an upper surface of the substrate and permits light emitted upwardly from the active layer 17 to be emitted through the top surface of the LED via the metal layer 21.
Here, when light emitted from the active layer 17 toward the sidewalls of the semiconductor layers reaches the sidewalls vertically formed as mentioned above, it is subjected to total reflection into the semiconductor layers with an increase in incident angle of the light instead of being easily emitted to air due to a difference in refractive index between the semiconductor layers and air, thereby decreasing the light emitting efficiency.